Kalilian-Shalamzari, M.

Pourmortazavi, S.M.

Rahimi-Nasrabadi, M.

Electronic Sumy State University Institutional Repository

Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   181  DETERMINATION OF THE OPTIMAL CONDITIONS  OF THE SYNTHESIS OF MANGANESE TUNGESTATE NANO-PATES Mehdi Rahimi-Nasrabadi1, Seied Mehdi Pourmortazavi2,  Morteza Kalilian-Shalamzari1  1 Department of Chemistry, Imam Hossein University, Tehran, Iran 2 Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran  ABSTRACT In this study, an orthogonal array design (OAD), OA9, was employed as a statisti-cal experimental method for the controllable, simple and fast synthesis of manganese tungestate nano-plates in flower-like clusters. Ultrafine manganese tungestate clusters were synthesized by a precipitation method involving the addition of manganese ion solution to the tungestate reagent. The effects of reaction conditions, i.e., manganese and tungestate concentrations, flow rate of reagent addition and temperature, on the diameter of the synthesized manganese tungestate nano-plates were investigated. The effects of these factors on the width of the manganese tungestate nano-plates were quantitatively evaluated by the analysis of variance (ANOVA). The results showed that manganese tungestate nano-plates can be synthesized by controlling the manganese and tungestate concentration and flow rate. Finally, the optimum conditions for the synthesis of man-ganese tungestate nano-plates by this simple and fast method were proposed. The results of ANOVA showed that 0.005 mol/L manganese ion concentration, 0.01 mol/L tung-estate ion concentration, 10 mL/min flow rate for the addition of the manganese reagent to the tungestate solution and 30 °C temperature are the optimum conditions for produc-ing manganese tungestate nano-plates with 50 ± 6 nm width.  INTRODUCTION There has been an increasing amount of interest in the synthesis of inor-ganic structures with nanoscale dimensions MnWO4 is a complex compound which has bulk electrical conductivity, relatively low melting point and novel magnetic property [1]. MnWO4 is highly sensitive to change in humidity [2] and having great potential to be used as high sensitivity humidity sensors [3,4], which are important for many industrial applications such as meteorology, medicine, food production, agriculture and the domestic environment [2]. It displays photoluminescence with two main bands at 421 and 438nm [5]. In addition, it has been reported that MnWO4 showed attractive  Various methods have been used to synthesis MnWO4, including hydro-thermal [6], solvothermal route [2], spray pyrolysis [1], cyclic microwave-assisted spray synthesis [1], precipitation synthesis [7,8], template synthesis [9] and solid state metathetic [10]. The purpose of this work was to produce 182                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I             MnWO4 nanoplates with flower-like clusters, using precipitation method, which is fast, simple and cost effective method. EXPERIMENTAL Analytical-grade Mn chloride and sodium tungstate were used as received from Merk. The MnWO4 particles were prepared by adding Mn2+ solution, at various concentrations and different flow rates, to the tungstate solution under vigorous stirring and various temperatures. After precipitation, the formed MnWO4 was filtered and washed with distilled water three times. The product was then washed with ethanol and dried at 70ºC for 2 h. To optimize experi-mental parameters for the synthesis MnWO4 particles, an experimental design approach was followed. The variables (Mn concentration, tungstate concentra-tion, flow rate of addition of Manganese reagent to the tungstate solution, and temperature) were as shown in Table  1. All samples were characterized by scanning electron microscopic (SEM) and energy-dispersive analysis by x-rays (EDAX). SEMs were recorded using on a Philips XL30 series instrument using a gold film for loading the dried particles on the instrument. Gold films were prepared by a Sputter Coater model SCD005 made by BAL-TEC (Switzerland).  Table 1 – Assignment  of  the  factors  and  levels  of  the  experiments  by  using  an  OA9 (34) matrix and mean width of manganese tungestate produced Experiment Number Mn2+ Concen-tration (M) WO42- Concen-tration (M) Mn2+ Feed flow rate (ml/min) Temperature (ƕC) Diameter of MnWO4 particles (nm) 1 0.005 0.005 2.5 0 78 2 0.01 0.005 10.0 30 58 3 0.1 0.005 40.0 60 64 4 0.005 0.01 10.0 60 78 5 0.01 0.01 40.0 0 80 6 0.1 0.01 2.5 30 91 7 0.005 0.1 40.0 30 60 8 0.01 0.1 2.5 60 83 9 0.1 0.1 10.0 0 66  RESULTS AND DISCUSSION Mixing the solutions of the anion and cation of an insoluble inorganic salt such as MnWO4 is a commonly used technology for synthesis many of water insoluble inorganic materials [11]. The control of particle size and shape is a complex process requiring a fundamental comprehensation of the interactions of reagents. The purpose of this study was to determine how the various parameters affect the diameter of MnWO4 nano-plates in flower-like clusters. The factors included in this study were Mn2+ and WO42- solution concentrations, flow rate for Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   183  addition of Mn2+ solution to the WO42- solution, and the temperature of the solu-tion. Factors and levels tested are reported in Table 1. The generated nano-plates clusters were characterized by X-ray powder diffraction and EDAX spectrum for the evaluation of their composition and purity. Figure 1 shows the XRD pattern of the obtained manganese tungestate nano-plates. All the diffraction peaks in the figure can be indexed to be in agreement with the hydrated structure of manganese tungestate (Moolooite) from PC-APD, Diffraction software.     Fig. 1 – XRD pattern of the MnWO4 nano-plates clusters prepared by precipitation method  Figure 2 shows the SEM images for four samples of MnWO4 obtained by this method. Also, data obtained by results of the experiments are given in Table 1.The FTIR spectra (Fig. 3) of MnWO4 with huebnerite structure show the inor-ganic modes in the range 556í983 cmí1 of the low wavenumber side at 912.30, 874.27, 810.16, 749.26, 652.15, 576.22 and 504.34 cmí1. The vibrations are in accordance with those of other researchers [5, 12]. These bands are assigned to be the internal stretching modes of Ȟ3(Au) and Ȟ3(Eu) transitions [5]. Fig. 3 shows the photoluminescence (PL) spectra of the present research. By using a 290 nm excitation wavelength, PL spectra show electronic transition within (WO4)í anion molecular complex, associated with the intrinsic emis-sion. It can be excited either in the excitonic absorption band or in the recombi-nation process [15], resulting from the huebnerite-structured products. 184                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                  (a) (b)       (c) (d) Fig. 2 – SEM images of MnWO4 nano-plates clusters obtained at different runs by  precipitation method: (a) run 1, (b) run 2, (c) run 4, and (d) run 7   Fig. 3 – PL spectra (292 nm excitation wavelength) of MnWO4 nano-plates clusters prepared with precipitation method 050100150200250300330 380 430 480 530IntensityWavelength (nm)Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   185  The emissions are blue spectra at 415–423 nm. Although the products were produced using different conditions. The results are in accordance with those detected by other researchers [5, 13]. CONCLUSIONS In  summary,  a  simple,  fast  and  controllable  method  for  the  synthesis  of  manganese tungestate nano-plates in flower-like clusters in aqueous media was explored. An OAD method was employed for the optimization of the reaction conditions. Some experimental parameters, such as manganese ion concentra-tion, tungestate concentration and flow rate were found to play significant roles in determining the particle size of the manganese tungestate nano-plates. The experiments proved that by using this method, the prediction of the optimum synthesis conditions of manganese tungestate nano-plates can be successfully performed. REFERENCES [1]  S. Thongtem, S. Wannapop, T. Thongtem, Trans. Nonferrous Met. Soc. China., 2009,Vol.19, P.100-104. [2] W.B. Hu, X.L. Nie, Y.Zh. Mi, Material Characterization, 2010, Vol.61, P.85–89. [3] W. Qu, W. Wlodarski, J.Meyer, Sensors and Actuators B, 2000, Vol.64, P.76–82. [4] U. Dellwo, P. Keller, J.U. Meyer Sens Actuators A, 1997, Vol.61, P.298–302. [5] S. Thongtem, S. Wannapop, A. Phuruangrat, T. Thongtem, Materials Letters, 2009, Vol.63, P.833–836. [6] L. Zhang, C. Lu, Y. Wang, Y. Cheng, Materials Chemistry and Physics, 2007, Vol.103, P.433–436. [7] T. Montini, V. Gombac, A. Hameed, L. Felisari, G. Adami, P. Fornasiero, Chemical Physics Letters, 2010, Vol.498, P.113–119. [8] H.Y. He, J.F. Huang, L.Y. Cao, J.P. Wu, Desalination, 2010, Vol.252, P.66–70. [9] H.  Zhou,  Y.  Yiu  ,  M.C.  Aronson,  S.S.  Wong,  Journal  of  Solid  State  Chemistry,  2008, Vol.181, P.1539– 1545. [10] P. Parhi, T.N. Karthik, V. Manivannan, Journal of Alloys and Compounds, 2008, Vol.465, P.380–386. [11] S.M. Pourmortazavi, S.S. Hajimirsadeghi, M. Rahimi-Nasrabadi, Chem. Eng. Comm., 2011, Vol.198, P.1182–1188. [12] B. Ingham, S.V. Chong, J.L. Tallon, Curr. Appl. Phys. 2006, Vol.6, P.553–6. [13] Y. Xing, S. Song, J. Feng, Y. Lei, M. Li, H. Zhang, Solid State Sci 2008, Vol.10, P.8.    

Determination of the optimal conditions of the synthesis of manganese tungestate nano-pates

SocioEconomic Challenges Journal (Sumy State University)

Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   181 
 
DETERMINATION OF THE OPTIMAL CONDITIONS  
OF THE SYNTHESIS OF MANGANESE TUNGESTATE 
NANO-PATES 
Mehdi Rahimi-Nasrabadi1, Seied Mehdi Pourmortazavi2,  
Morteza Kalilian-Shalamzari1 
 
1 Department of Chemistry, Imam Hossein University, Tehran, Iran 
2 Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, 
Tehran, Iran 
 
ABSTRACT 
In this study, an orthogonal array design (OAD), OA9, was employed as a statisti-
cal experimental method for the controllable, simple and fast synthesis of manganese 
tungestate nano-plates in flower-like clusters. Ultrafine manganese tungestate clusters 
were synthesized by a precipitation method involving the addition of manganese ion 
solution to the tungestate reagent. The effects of reaction conditions, i.e., manganese and 
tungestate concentrations, flow rate of reagent addition and temperature, on the diameter 
of the synthesized manganese tungestate nano-plates were investigated. The effects of 
these factors on the width of the manganese tungestate nano-plates were quantitatively 
evaluated by the analysis of variance (ANOVA). The results showed that manganese 
tungestate nano-plates can be synthesized by controlling the manganese and tungestate 
concentration and flow rate. Finally, the optimum conditions for the synthesis of man-
ganese tungestate nano-plates by this simple and fast method were proposed. The results 
of ANOVA showed that 0.005 mol/L manganese ion concentration, 0.01 mol/L tung-
estate ion concentration, 10 mL/min flow rate for the addition of the manganese reagent 
to the tungestate solution and 30 °C temperature are the optimum conditions for produc-
ing manganese tungestate nano-plates with 50 ± 6 nm width. 
 
INTRODUCTION 
There has been an increasing amount of interest in the synthesis of inor-
ganic structures with nanoscale dimensions MnWO4 is a complex compound 
which has bulk electrical conductivity, relatively low melting point and novel 
magnetic property [1]. MnWO4 is highly sensitive to change in humidity [2] 
and having great potential to be used as high sensitivity humidity sensors [3,4], 
which are important for many industrial applications such as meteorology, 
medicine, food production, agriculture and the domestic environment [2]. It 
displays photoluminescence with two main bands at 421 and 438nm [5]. In 
addition, it has been reported that MnWO4 showed attractive  
Various methods have been used to synthesis MnWO4, including hydro-
thermal [6], solvothermal route [2], spray pyrolysis [1], cyclic microwave-
assisted spray synthesis [1], precipitation synthesis [7,8], template synthesis [9] 
and solid state metathetic [10]. The purpose of this work was to produce 
182                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I            
 
MnWO4 nanoplates with flower-like clusters, using precipitation method, 
which is fast, simple and cost effective method. 
EXPERIMENTAL 
Analytical-grade Mn chloride and sodium tungstate were used as received 
from Merk. The MnWO4 particles were prepared by adding Mn2+ solution, at 
various concentrations and different flow rates, to the tungstate solution under 
vigorous stirring and various temperatures. After precipitation, the formed 
MnWO4 was filtered and washed with distilled water three times. The product 
was then washed with ethanol and dried at 70ºC for 2 h. To optimize experi-
mental parameters for the synthesis MnWO4 particles, an experimental design 
approach was followed. The variables (Mn concentration, tungstate concentra-
tion, flow rate of addition of Manganese reagent to the tungstate solution, and 
temperature) were as shown in Table  1. All samples were characterized by 
scanning electron microscopic (SEM) and energy-dispersive analysis by x-rays 
(EDAX). SEMs were recorded using on a Philips XL30 series instrument using 
a gold film for loading the dried particles on the instrument. Gold films were 
prepared by a Sputter Coater model SCD005 made by BAL-TEC (Switzerland). 
 
Table 1 – Assignment  of  the  factors  and  levels  of  the  experiments  by  using  an  
OA9 (34) matrix and mean width of manganese tungestate produced 
Experiment 
Number 
Mn2+ Concen-
tration (M) 
WO42- Concen-
tration (M) 
Mn2+ Feed flow 
rate (ml/min) 
Temperature 
(?C) 
Diameter of 
MnWO4 
particles (nm) 
1 0.005 0.005 2.5 0 78 
2 0.01 0.005 10.0 30 58 
3 0.1 0.005 40.0 60 64 
4 0.005 0.01 10.0 60 78 
5 0.01 0.01 40.0 0 80 
6 0.1 0.01 2.5 30 91 
7 0.005 0.1 40.0 30 60 
8 0.01 0.1 2.5 60 83 
9 0.1 0.1 10.0 0 66 
 
RESULTS AND DISCUSSION 
Mixing the solutions of the anion and cation of an insoluble inorganic salt 
such as MnWO4 is a commonly used technology for synthesis many of water 
insoluble inorganic materials [11]. The control of particle size and shape is a 
complex process requiring a fundamental comprehensation of the interactions of 
reagents. The purpose of this study was to determine how the various parameters 
affect the diameter of MnWO4 nano-plates in flower-like clusters. The factors 
included in this study were Mn2+ and WO42- solution concentrations, flow rate for 
Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   183 
 
addition of Mn2+ solution to the WO42- solution, and the temperature of the solu-
tion. Factors and levels tested are reported in Table 1. 
The generated nano-plates clusters were characterized by X-ray powder 
diffraction and EDAX spectrum for the evaluation of their composition and 
purity. Figure 1 shows the XRD pattern of the obtained manganese tungestate 
nano-plates. All the diffraction peaks in the figure can be indexed to be in 
agreement with the hydrated structure of manganese tungestate (Moolooite) 
from PC-APD, Diffraction software.  
 
 
 
Fig. 1 – XRD pattern of the MnWO4 nano-plates clusters prepared by precipitation 
method 
 
Figure 2 shows the SEM images for four samples of MnWO4 obtained by 
this method. Also, data obtained by results of the experiments are given in Table 
1.The FTIR spectra (Fig. 3) of MnWO4 with huebnerite structure show the inor-
ganic modes in the range 556?983 cm?1 of the low wavenumber side at 912.30, 
874.27, 810.16, 749.26, 652.15, 576.22 and 504.34 cm?1. The vibrations are in 
accordance with those of other researchers [5, 12]. These bands are assigned to be 
the internal stretching modes of ?3(Au) and ?3(Eu) transitions [5]. 
Fig. 3 shows the photoluminescence (PL) spectra of the present research. 
By using a 290 nm excitation wavelength, PL spectra show electronic transition 
within (WO4)?? anion molecular complex, associated with the intrinsic emis-
sion. It can be excited either in the excitonic absorption band or in the recombi-
nation process [15], resulting from the huebnerite-structured products. 
184                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I            
 
    
 (a) (b) 
     
 (c) (d) 
Fig. 2 – SEM images of MnWO4 nano-plates clusters obtained at different runs by 
 precipitation method: (a) run 1, (b) run 2, (c) run 4, and (d) run 7 
 
 
Fig. 3 – PL spectra (292 nm excitation wavelength) of MnWO4 nano-plates clusters 
prepared with precipitation method 
0
50
100
150
200
250
300
330 380 430 480 530
In
te
ns
ity
Wavelength (nm)
Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   185 
 
The emissions are blue spectra at 415–423 nm. Although the products 
were produced using different conditions. The results are in accordance with 
those detected by other researchers [5, 13]. 
CONCLUSIONS 
In  summary,  a  simple,  fast  and  controllable  method  for  the  synthesis  of  
manganese tungestate nano-plates in flower-like clusters in aqueous media was 
explored. An OAD method was employed for the optimization of the reaction 
conditions. Some experimental parameters, such as manganese ion concentra-
tion, tungestate concentration and flow rate were found to play significant roles 
in determining the particle size of the manganese tungestate nano-plates. The 
experiments proved that by using this method, the prediction of the optimum 
synthesis conditions of manganese tungestate nano-plates can be successfully 
performed. 
REFERENCES 
[1]  S. Thongtem, S. Wannapop, T. Thongtem, Trans. Nonferrous Met. Soc. China., 
2009,Vol.19, P.100-104. 
[2] W.B. Hu, X.L. Nie, Y.Zh. Mi, Material Characterization, 2010, Vol.61, P.85–89. 
[3] W. Qu, W. Wlodarski, J.Meyer, Sensors and Actuators B, 2000, Vol.64, P.76–82. 
[4] U. Dellwo, P. Keller, J.U. Meyer Sens Actuators A, 1997, Vol.61, P.298–302. 
[5] S. Thongtem, S. Wannapop, A. Phuruangrat, T. Thongtem, Materials Letters, 2009, 
Vol.63, P.833–836. 
[6] L. Zhang, C. Lu, Y. Wang, Y. Cheng, Materials Chemistry and Physics, 2007, 
Vol.103, P.433–436. 
[7] T. Montini, V. Gombac, A. Hameed, L. Felisari, G. Adami, P. Fornasiero, Chemical 
Physics Letters, 2010, Vol.498, P.113–119. 
[8] H.Y. He, J.F. Huang, L.Y. Cao, J.P. Wu, Desalination, 2010, Vol.252, P.66–70. 
[9] H.  Zhou,  Y.  Yiu  ,  M.C.  Aronson,  S.S.  Wong,  Journal  of  Solid  State  Chemistry,  
2008, Vol.181, P.1539– 1545. 
[10] P. Parhi, T.N. Karthik, V. Manivannan, Journal of Alloys and Compounds, 2008, 
Vol.465, P.380–386. 
[11] S.M. Pourmortazavi, S.S. Hajimirsadeghi, M. Rahimi-Nasrabadi, Chem. Eng. 
Comm., 2011, Vol.198, P.1182–1188. 
[12] B. Ingham, S.V. Chong, J.L. Tallon, Curr. Appl. Phys. 2006, Vol.6, P.553–6. 
[13] Y. Xing, S. Song, J. Feng, Y. Lei, M. Li, H. Zhang, Solid State Sci 2008, Vol.10, 
P.8. 
 
  


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Determination of the optimal conditions of the synthesis of manganese tungestate nano-pates

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